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Title: getenv(3) - Linux manual page Authors: Venue: man Year: 2008 Canonical: man:man3/getenv.3 URL: https://man7.org/linux/man-pages/man3/getenv.3.html Collector: man OA: true ABSTRACT getenv(3) - Linux manual page man7.org Linux man-pages Linux/UNIX system programming training getenv(3) — Linux manual page NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON getenv(3) Library Functions Manual getenv(3) NAME top getenv, secure_getenv - get an environment variable LIBRARY top Standard C library (libc, -lc) SYNOPSIS top #include char *getenv(const char *name); char *secure_getenv(const char *name); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): secure_getenv(): _GNU_SOURCE DESCRIPTION top The getenv() function searches the environment list to find the environment variable name, and returns a pointer to the corresponding value string. The secure_getenv() function is just like getenv() except that it returns NULL in cases where "secure execution" is required. Secure execution is required if one of the following conditions was true when the program run by the calling process was loaded: • the process's effective user ID did not match its real user ID or the process's effective group ID did not match its real group ID (typically this is the result of executing a set-user- ID or set-group-ID program); • the effective capability bit was set on the executable file; or • the process has a nonempty permitted capability set. Secure execution may also be required if triggered by some Linux security modules. The secure_getenv() function is intended for use in general- purpose libraries to avoid vulnerabilities that could occur if set-user-ID or set-group-ID programs accidentally trusted the environment. RETURN VALUE top The getenv() function returns a pointer to the value in the environment, or NULL if there is no match. ATTRIBUTES top For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────────────────┬───────────────┬─────────────┐ │ Interface │ Attribute │ Value │ ├──────────────────────────────────┼───────────────┼─────────────┤ │ getenv(), secure_getenv() │ Thread safety │ MT-Safe env │ └──────────────────────────────────┴───────────────┴─────────────┘ STANDARDS top getenv() C11, POSIX.1-2008. secure_getenv() POSIX.1-2024. HISTORY top getenv() POSIX.1-2001, C89, C99, SVr4, 4.3BSD. secure_getenv() POSIX.1-2024, glibc 2.17. NOTES top The strings in the environment list are of the form name=value. As typically implemented, getenv() returns a pointer to a string within the environment list. The caller must take care not to modify this string, since that would change the environment of the process. The implementation of getenv() is not required to be reentrant. The string pointed to by the return value of getenv() may be statically allocated, and can be modified by a subsequent call to getenv(), putenv(3), setenv(3), or unsetenv(3). The "secure execution" mode of secure_getenv() is controlled by the AT_SECURE flag contained in the auxiliary vector passed from the kernel to user space. SEE ALSO top clearenv(3), getauxval(3), putenv(3), setenv(3), unsetenv(3), capabilities(7), environ(7) COLOPHON top This page is part of the man-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.19.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2026-09-09. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Linux man-pages 6.19 2026-02-08 getenv(3) Pages that refer to this page: clearenv(3), getauxval(3), libsystemd(3), libudev(3), pmgetconfig(3), putenv(3), sd-bus(3), sd_bus_add_match(3), sd_bus_add_node_enumerator(3), sd_bus_add_object(3), sd_bus_add_object_manager(3), sd_bus_attach_event(3), sd_bus_call(3), sd_bus_call_method(3), sd_bus_can_send(3), sd_bus_close(3), sd_bus_creds_get_pid(3), sd_bus_creds_new_from_pid(3), sd_bus_default(3), sd_bus_emit_signal(3), sd_bus_enqueue_for_read(3), sd_bus_error(3), sd_bus_error_add_map(3), sd-bus-errors(3), sd_bus_get_current_handler(3), sd_bus_get_fd(3), sd_bus_get_name_creds(3), sd_bus_get_name_machine_id(3), sd_bus_get_n_queued_read(3), sd_bus_interface_name_is_valid(3), sd_bus_is_open(3), sd_bus_list_names(3), sd_bus_message_append(3), sd_bus_message_append_array(3), sd_bus_message_append_basic(3), sd_bus_message_append_string_memfd(3), sd_bus_message_append_strv(3), sd_bus_message_at_end(3), sd_bus_message_copy(3), sd_bus_message_dump(3), sd_bus_message_get_cookie(3), sd_bus_message_get_monotonic_usec(3), sd_bus_message_get_signature(3), sd_bus_message_get_type(3), sd_bus_message_new(3), sd_bus_message_new_method_call(3), sd_bus_message_new_method_error(3), sd_bus_message_new_signal(3), sd_bus_message_open_container(3), sd_bus_message_read(3), sd_bus_message_read_array(3), sd_bus_message_read_basic(3), sd_bus_message_read_strv(3), sd_bus_message_rewind(3), sd_bus_message_seal(3), sd_bus_message_sensitive(3), sd_bus_message_set_destination(3), sd_bus_message_set_expect_reply(3), sd_bus_message_skip(3), sd_bus_message_verify_type(3), sd_bus_negotiate_fds(3), sd_bus_new(3), sd_bus_path_encode(3), sd_bus_pending_method_calls(3), sd_bus_process(3), sd_bus_query_sender_creds(3), sd_bus_reply_method_error(3), sd_bus_reply_method_return(3), sd_bus_request_name(3), sd_bus_send(3), sd_bus_set_address(3), sd_bus_set_close_on_exit(3), sd_bus_set_connected_signal(3), sd_bus_set_description(3), sd_bus_set_exit_on_disconnect(3), sd_bus_set_fd(3), sd_bus_set_method_call_timeout(3), sd_bus_set_property(3), sd_bus_set_sender(3), sd_bus_set_server(3), sd_bus_set_watch_bind(3), sd_bus_slot_get_bus(3), sd_bus_slot_ref(3), sd_bus_slot_set_description(3), sd_bus_slot_set_destroy_callback(3), sd_bus_slot_set_floating(3), sd_bus_slot_set_userdata(3), sd_bus_start(3), sd_bus_track_add_name(3), sd_bus_track_new(3), sd_bus_wait(3), sd-daemon(3), sd-device(3), sd_device_get_syspath(3), sd-event(3), sd_event_add_child(3), sd_event_add_defer(3), sd_event_add_inotify(3), sd_event_add_io(3), sd_event_add_memory_pressure(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_exit(3), sd_event_get_fd(3), sd_event_new(3), sd_event_now(3), sd_event_run(3), sd_event_set_exit_on_idle(3), sd_event_set_signal_exit(3), sd_event_set_watchdog(3), sd_event_source_get_event(3), sd_event_source_get_pending(3), sd_event_source_set_description(3), sd_event_source_set_destroy_callback(3), sd_event_source_set_enabled(3), sd_event_source_set_exit_on_failure(3), sd_event_source_set_floating(3), sd_event_source_set_prepare(3), sd_event_source_set_priority(3), sd_event_source_set_ratelimit(3), sd_event_source_set_userdata(3), sd_event_source_unref(3), sd_event_wait(3), sd_get_seats(3), sd-hwdb(3), sd_hwdb_get(3), sd_hwdb_new(3), sd-id128(3), sd_id128_get_machine(3), sd_id128_randomize(3), sd_id128_to_string(3), sd-journal(3), sd_journal_add_match(3), sd_journal_print(3), sd-json(3), sd_json_dispatch_string(3), sd_json_parse(3), sd_listen_fds(3), sd-login(3), sd_login_monitor_new(3), sd_machine_get_class(3), sd_notify(3), sd-path(3), sd_path_lookup(3), sd_seat_get_active(3), sd_session_is_active(3), sd_uid_get_state(3), sd-varlink(3), sd_varlink_call_and_upgrade(3), sd_varlink_connect_address(3), sd_varlink_is_connected(3), sd_varlink_push_fd(3), sd_varlink_reply_and_upgrade(3), sd_varlink_send(3), sd_varlink_server_listen_address(3), sd_varlink_server_new(3), sd_varlink_set_description(3), sd_varlink_set_relative_timeout(3), sd_watchdog_enabled(3), setenv(3), tzset(3), attributes(7), environ(7), rpm-lua(7), rpm-macros(7) HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. 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